If you’ve opened a bottle of Advil or Tylenol in the last few decades you know how much of a pain it can be.
First there’s the safety cap, then the wad of cotton, and they’re all kept underneath a child-proof lock that’s tough for most adults to open.
But none of those safety precautions existed when the Tylenol Murderer terrorized the country.
The string of killings baffle detectives to this day, and the man behind them could still be on the loose.
It all started when 12-year-old Mary Kellerman from Chicago told her parents she had a cold. They gave her Tylenol, and just minutes later the young girl collapsed.
Within hours, Kellerman was dead. But she was only the first victim in a string of deaths across Chicago in 1982.
Six more victims soon died under similar circumstances.
One victim was a mother of four. One was a flight attendant.
The only thing connecting their cases were Tylenol pills, taken shortly before death.
In one family, three victims died one after another after taking pills from the same bottle: first one man, then his brother, then the brother's wife.
Once police identified the connections they began to trace back the poisoned pills.
Each bottle of pills had been laced with an enormous dose of potassium cyanide, enough to kill thousands of people each.
An investigator from Cook County's medical examiner's office remembered opening one of the fatal bottles:
"Nothing looked out of the ordinary. However, as I was pouring them out of the bottles, I could tell there was a strong smell of almonds."
An investigation revealed that the bottles had been sold at different stores and manufactured at different plants.
It seemed the poisoner had taken the bottles, tampered with them, then replaced them on store shelves across Chicago.
Johnson & Johnson, the makers of Tylenol, began a massive nationwide recall.
Hospitals were warned to stop using Tylenol, and 31 million bottles - worth over $100 million - were recalled.
But the investigation into the poisonings stalled. Police found three more tampered bottles, but no clues leading to the murderer.
But while this case is still unsolved, there are a number of famous suspects - including a convicted terrorist.
The first major suspect in the Tylenol Murders was James W. Lewis.
Lewis was a tax consultant who had a famous run-in with the law before the pill poisonings began.
Lewis had been charged with murder in 1978, after police discovered the chopped-up remains of one of his clients in his home. Police were later forced to drop the charges because their search of his home was illegal.
During the poisonings, Lewis wrote a letter to Johnson & Johnson, demanding a $1 million ransom to make the killings stop.
While Lewis was convicted of extortion over the letter, he and his wife were in New York during the poisonings, and were never charged with the murders.
The Unabomber, Ted Kaczynski, was also considered a suspect when police re-opened the poisoning case a few years ago.
Kaczynski was raised in Chicago during the murders, before making international headlines as a serial bomber who targeted universities.
A DNA test based on evidence from the tampered bottles ruled out Kaczynski.
One twist in the case came in 2011, when a Johnson & Johnson whistle-blower named Scott Bartz questioned one of the case's central theories.
Bartz alleged that the Tylenol had not been tampered with after it was shipped to stores. Instead, he claimed it had been poisoned during the company's own repackaging process.
Chicago police still hope that DNA evidence could finally solve this cold case, decades later.
There was one upside to this tragedy: it lead to tougher laws for tamper-proof medicine containers.
After the Chicago murders - and hundreds of copycat poisonings across the country - Congress passed the "Tylenol Bill," which made tampering a federal offense.
The FDA updated their requirements for tamper-proof bottles in 1989, and we've been struggling to get them open ever since.
Still, it's better than worrying about cyanide lurking in our pain pills.
Did you know about this terrifying case?